The present invention relates to generators for use in micro-electro-mechanical systems, and particularly to a micro-electro-mechanical generator designed to generate electricity by allowing a portion of a fluid chamber charged with fluid to be moved reciprocally.
A micro-electro-mechanical system (MEMS) is one wherein mechanical components and electronic components are incorporated together in a very small size ranging from several micrometers to dozens of millimeters. In a MEMS, a number of elements requiring electricity such as micro-pumps, microprocessors, micro-sensors, micro-actuators, etc., are integrated with one another. Although voltage and current required to drive these elements of the MEMS are very minute in magnitude compared to those consumed in macro-scaled systems, it is difficult for a power supply for the elements in the MEMS to generate a proper level of the voltage and the current, as it must be very small in size for use in the micro-scaled system.
Conventionally, supply of power for known MEMS has been achieved by using a fuel cell and, in some cases, the power has been supplied to the MEMS in the form of microwaves. More recently, a need has been identified for a semi-permanent system that generates electricity by using an external environment having a temperature difference, without necessitating an external power source. The need for a semi-permanent, self-electricity generating system leads to a study on an autonomous MEMS which would mean a system operable semi-permanently in a condition isolated and independent from an external system.
In a known power generator for use in a macro-scaled system, a high temperature section and a low temperature section are provided. Working fluid is sequentially passed between the two sections in such a manner that the fluid is heated in the high temperature section to work outside, then cooled by the low temperature section, and is returned to the high temperature, repeatedly. The problem in the art is that it is difficult to apply this principle to a generator for a MEMS due to limitations in volume, a limitation in the relevant micro-fabrication technology, and influences to other electric circuits or electronic circuit components which have to be incorporated with the generator in the MEMS.
Thermoelectric modules have also been used for power generation in a MEMS. Power generation using the thermoelectric module adapts the Seebeck-effect wherein two different metals are joined to each other and a temperature difference is applied between them to induce a current.
The thermoelectric module is simple in configuration and when it operates under a small temperature difference condition it can generate electricity commensurate to that small temperature difference. The thermoelectric module could appear to provide a generator suitable for application with the MEMS as a stable energy source with its advantages including operation with reduced noise as it requires no working fluid or parts performing mechanical movement.
However, this type of generator has low operational efficiency and cannot generate sufficient levels of current and voltage. For these reasons, this type of generator is not an appropriate power source for a micro-pump for the MEMS.
There is a need in the art for a micro-electro-mechanical generator capable of providing appropriate levels of electricity for MEMS at levels greater than known MEMS generators.
It is, therefore, an object of the present invention to provide a micro-electro-mechanical generator capable of providing increased levels of electricity with respect to levels provided by known MEMS generators.
The object and other objects, which will become apparent to those skilled in the art, are accomplished with a micro-electro-mechanical generator, comprising a housing, a heating means and a cooling means disposed within the housing, with the cooling means opposite to the heating means. A heat transfer member is positioned between the heating means and cooling means, with the heat transfer member having a first surface facing the heating means and a second surface facing the cooling means.
A supporting member supports the heat transfer member at an external portion of the heat transfer member and is alternatively deformable between a first position wherein the heat transfer member is adjacent the heating means, and a second position wherein the heat transfer member is adjacent the cooling means. The supporting member partitions the housing into a sealed first space at a side of the heating means and a second space at a side of the cooling means. The sealed first space and the second spaces are respectively adapted to be charged with a first fluid and a second fluid. The supporting member is alternatively deformed in a bi-stable snapping action wherein the first position and the second position of the supporting member are two stable positions.
A power-generating means generates electricity by using the alternative deforming action by the supporting member. The power-generating means can comprise a piezoelectric element provided in the supporting member. The power-generating means can also comprise the heat transfer member and a coil disposed in the housing, wherein the heat transfer member is a permanent magnet. The first fluid is heated by the heating means to its boiling point and is cooled by the cooling means to condensation. The heat transfer member can further comprise a plurality of pins which maintain the first fluid in a liquid state with a capillary action therebetween. The first fluid is selected from the group consisting of pentane and HFC-134a.